Lasting effects of chronic fluoxetine treatment on the late developing rat brain: Age-dependent changes in the serotonergic neurotransmitter system assessed by pharmacological MRI

► We performed 5-HT phMRI in chronic fluoxetine-treated juvenile and adult rats. ► Juvenile treatment caused an opposite phMRI response compared to adult treatment. ► An age by treatment interaction effect was seen in 5-HT related brain regions. ► Our findings probably reflect neuronal imprinting effects of early SSRI treatment. ► phMRI is suitable to non-invasively assess age-related differences in 5-HT response.